滇西兰坪盆地金顶铅锌矿盐构造发育特征及其与成矿关系

滇西兰坪中新生代盆地广泛发育盐岩层系。通过对金顶超大型铅锌矿区的露天采厂和地下采坑的最新野外调查及大量钻孔资料的综合分析,研究区盐岩层系具有多期、多阶段运动的特点,厚度分布极不均一,它们作为区域推覆构造作用的滑脱层,对盐上层构造变形起着重要控制作用,形成一系列储矿构造。研究表明,矿区盐构造主要包括盐枕、盐背斜、盐焊接、盐穿刺、盐推覆、盐岩滑脱-断层相关褶皱组合等多种盐构造变形样式。这些盐构造的形成演化及变形机制主要受到推覆挤压缩短作用、基底断层作用和塑性流动汇聚作用、盐下和盐上层断裂滑脱作用等控制,主要沿推覆断裂构造带呈串珠状分布。金项矿区盐构造分为两个阶段:古新世–始新世挤压–拗陷层内变形阶段,形成盐枕、隆升较低的盐背斜等整合型盐构造;渐新世的逆冲推覆–盐岩滑脱阶段,受强烈的挤压推覆作用而形成盐墙、盐株等盐穿刺型构造。盐构造不同阶段的变形演化对金属元素富集成矿起到关键作用,其流动变形而形成的盐构造圈闭促使了金属聚集成矿。

Characteristics of Salt Structures and Links to Pb-Zn Mineralization of the Jinding Deposit in Lanping Basin,Western Yunnan

The salt rocks are widespread in the Lanping Mesozoic-Cenozoic basin. The up to date open pit and underground investigations, and comprehensive analyses of the massive borehole data in the Jinding super large Pb-Zn deposit, show that the thickness of salt beds is very heterogeneous, with characteristics of multi-period and multi-stage features. Being the decollement layers of regional nappe structure, the salt rock played an important role in controlling the suprasalt tectonic deformation and supplied spaces for ore deposition. Salt structures in the Jinding deposit include salt pillows, salt anticlines, salt welds, salt diapirs, salt nappes, and salt decollement layers-fault. The salt structures were mainly controlled by the short-range pushing and squeezing, basal faulting, plastic flowing and convergence, and decollement fault of subsalt and suprasalt. These salt structures distribute along with the nappe structure belts like a string of beads. The salt structures in the Jinding deposit were divided into two stages, compressional depressing stage deformation inside of the Paleocene-Eocene layers including the salt pillows and salt anticlines. The Oligocene thrust nappe-decollement stage salt diapiric structures including salt walls and salt stocks by strongly compressing and napping. The salt structures played a key role in migration of ore metals and provided spaces for the ore mineralization.